Catalytic conversion of hydrocarbons



Patented Nov. 11, 194? CATALYTIC CONVERSION OF HYDROCARBONS Frederick E. Bay, Mantua, Russell Lee, Wenonah, N. 3., and Jacob R. Meadow, Memphis, Tenn., assignors to Socony-Vacuum Oil Company, Incorporated, a corporation of New York No Drawing. Application November 29, 1944, Serial No. 565,786

This invention relates to, processes for conversion of hydrocarbons wherein the vapors of a hydrocarbon charge stock are contacted at conversion conditions of temperature and pressure with generation differ in the time factor as well as in the nature of the change occurring. Coke deposition, which will be hereinafter called contamination, is fairly rapid, it being desirable to a solid adsorbent conversion catalyst containing remove the coke by burning after about 10 to 20 silica and an oxide of a metal which is diflicult minutes on stream. This burning of the coke to reduce, for example, alumina, beryllia, zirwill b hereinafter designated as "regeneration. conia, titania and the like. More specifically the On the other hand, the change in basic nature invention is concerned, in certain preferred emof the catalyst; resulting in lowered activity after bodiments, with a process of that type in which 10 regeneration, is a slow change. A catalyst may a catalyst which has suffered serious deteriorabe in service for over a year of thirty minute tion of activity is reactivated by a novel method cycles before becoming so degenerated as to reof treatment thereinafter described. quire replacement. For example, a year or more Processes of catalytic conversion of the type to may elapse before a catalyst in continuous servwhich this invention pertains are well known in ice drops from an initial activity of 45, as herethe art. Outstanding examples are catalytic inafter defined, to 25 or 30. This slow degeneracracking and catalytic reforming, usually on siltion will be referred to herein as deactivation" ica-alumina, although composites of silica with to distinguish it from contamination. a difiicultly reducible metal oxide in general have It is the primary object of this invention to rebeen shown to be active. Catalytic cracking on turn a deactivated catalyst to a higher activity silica-alumina composites may be taken as typilevel by contacting a hydrocarbon vapor containcal for purposes of showing the objects and ading organic fluorides with the deactivated catalyst vantages of the invention. under conversion conditions of temperature and In processes of catalytic cracking, a composite pressure. Processes of this nature wherein the of the class defined above, e. g., a porous adorganic fluorides result from treatment of the sorbent clay or synthetic composite of silica and charge stock with hydrogen fluoride are claimed alumina, is contacted with hydrocarbon vapors in the copending application 01' Jacob R. Meadow, at conversion conditions, sa 800 to 1000 F. at Serial No. 565,785, flied November 29, 1944. This atmospheric or greater pressure. The reaction treatment of the catalyst to raise the activity will which takes place is essentially a cracking to be designated "reactivation to avoid confusion produce lighter hydrocarbons but is accompanied with regeneration" by burning of a combustible by a number of complex side reactions such as deposit. aromatization, polymerization, alkyiation, etc. As -The nature of the deactivation is not undera result of these complex reactions, a carbonastood and it is, therefore, impossible to afford a ceous deposit is laid downon the catalyst which clear explanation of reactivation as practiced acis commonly called "coke," although it contains cording to this invention. It has been noted that considerable hydrogen and is probably a high- X-ray diffraction patterns show crystalline matly condensed hydrocarbon. The coke tends to ter in catalyst deactivated by aging and it may seriousl impair the catalytic emciency of the be that high catalyt c a t y is o t d with catalyst for the principal reaction and the con the amorphous state. On that assumption, it may version reaction is therefore suspended aftercoke, be postulated that reactivation with alkyl fluoride to the extent of a few per cent by weight of catacauses reversion of crystalline matter to an lyst, has accumulated on the catalyst. The cataamorphous form which is more active. How lytic surface is then regenerated by burning the it may also be suggested that the reactivation is coke in a stream of oxidizing gas and the amdue, not to a return of the catalyst to its original lyst is returned to the conversion stage of the form, but to formation of active compounds such cycle. as aluminum fluoride, silicon tetrafluoride which The catalyst also undergoes a second type of reacts with aluminumoxide to form a non-voladegeneration by reason of changes in the catalyst tfle complex, or the like. If that be the true exitself, as contrasted with the masking of catalytic planation, the reactivation is, in efl'ect, the consurfaces by a coke deposit. As the catalyst is version of deactivated catalyst to anew composicarried through a large number of cycles of altion of matter differing in chemical nature from ternate conversion and regeneration, the activity but similar inactivity to the original catalyst. following each regeneration becomes progres-' The invention is, of course, not limited to any sively less until the activity is too lo'wfor economitheory of operation, but it is believed that the cal use of the catalyst. These two types of deeflects obtained are due to the presence in the conversion zone of nascent hydrogen fluoride form by catalytic decomposition of the organic fluorides. Eflects of somewhat the same general nature may be obtained by the use of hydrogen 4 In some instances, the gasoline to coke ratio appears to be adversely aflected by extensive treatment for reactivation. In connection with catalysts sensitive to overtreatment, suitable care flu ri e 8 ut t ppears to be undesirable 5 should be exercised. It is noted that most catin that hydrogen fluoride so introduced is less efalysts do not show such sensitivity under condiiective when used in amounts and under conditions employed so far. tions to avoid substantial decomposition of the The benefits of the invention are illustrated by catalyst. It appears that small amounts or nasa series of cycles in which a catalyst was t cent hyd o n fl r f that be the active pr 10 nately on stream for conversion of gas oil at 800 cipal, are vastly superior to hydrogen fluoride F. and atmospheric pressure and in regeneration introduced such- 1 for burning of coke. During the conversion side The amount of organic fluoride introduced acof the cycle, oil was supplied at a space velocity cording to the present invention should be kept of 1.5 volumes of liquid oil per volume of catalyst relatively low. In general, less than 1% by weight per hour and one volume of liquid oil was conbased on total vapor charge of fluorine in the tacted with four volumes of catalyst during each form of organic fluoride is preferred. Larger cycle. The catalyst was a synthetic silica-alumiamounts up to about 3% may be used, but withma ccprecipitate. During certain of the cycles, out marked advantage. When still larger amounts the charge stock supplied (treated gas oil) was of fluorides are present, the treatment tends to gas oil which had been treated with hydrogen cause serious damage to the catalyst. The prefluoride in liquid phase to separate sulfur and ferred procedure is to conduct the fluoride conasphaltic compounds while propylene was added taining vapor over the catalyst in the same man during such treatment with hydrogen fluoride to ner and under the same conditions as those emfl y compounds in the charge susceptible to ployed for conducting the principal reaction. a ylation. Preferably, the treatment is made in a plurality The yields obtained on treated gas oil are of cycles with a hydrocarbon fraction containing not necessarily comparable with each other or a very small amount of fluorides; for example, with yields on standard gas oil" because of difup to about 0.3% fluorine by weight. It is to be ferences in nature and history of the charge. understood that use of the term "cycle in the The significant values are the yields on standard specification is not intended to refer only to fixed gas oil which is the gas oil out of Oklahoma City bed operation wherein hydrocarbons and regencrude. The yield of gasoline from the standard eration air are alternately passed through a stacharge is regarded as the index of activity of tionary mass of catalyst. Continuous operations the catalyst. in which the catalyst passes alternately through Table I below shows the results obtained.

TABLE I Activation of fresh catalyst Cracking Yields Charge Stock, No. 01 410F.

Description Per Cent Cycles or Cycles Gas, Coke, E.P. Gasoline Gasoline wt. PerCent PerCent Gasoline, to Coke to Gas wt. wt. Per Cent Ratio Ratio vol.

Standard G8! on Nil 3 s 0.5 2.0 43.0 14.8:1 0.1m 0.19 5 13 11.5 4.5 38.4 8.5:1 3.11:1 0.01 1 20 0.2 4.4 44.4 mm 1.2=1 5 25 11.0 3.1 40.0 10.s=1 3.5a Nil 0 30 5.0 3.0 45.0 1am 1.1m 0.11 s 35 12.0 3.0 41.0 10.1=1 3.311 0.13 4 30 16.6 5.0 40.0 8.121 24:11 0.00 5 44 8.7 4.0 40.4 mm 5.21 no 0.01 a 49 1.3 4.1 41.3 mm 0.0a Standard Gas 011 Nil 5 54 0.5 a. 4 49.1 14.011 1.111

a reaction zone for contact with charge and a The above table shows significant increases in regeneration zone are well adapted to the puractivity when a relatively active catalyst is used. poses of the invention. In the latter case, a cycle The invention may thus be used to activate fresh indicates the average interval required for cat- (10 catalyst. However, the treatment is somewhat alyst to complete the circuit through reactor and drastic when compared to the increase in activregenerator. Fixed bed runs reflect the advanity of the catalyst. Catalysts activated accordtages of the invention more accurately since ing to the present invention show a faster rate of each catalyst particle is contacted in the same decrease in activity during use than catalysts not manner during successive cycles, and the results 6., so activated, and it is believed that the principal reported herein are of that type. value of the invention is restoration of the activ- The ratio between the time a catalyst may be ity of the catalyst which has become deactivated employed for cracking and the time s ent in regenover a long period of use. Such deactivated cateratlonisafunction of the rate of coke formation. alyst was used in a series of cycles similar to Thus a catalyst which forms twice as much coke those of Table I. The catalyst was similar to is actually only half as efllcient as the standard, that of Table I except that it had been in service although both catalysts may have the same acin a commercial unit for a period of time suflltivity" as measured by percent conversion of gas cient to decrease its acitvity to 28.3. The results oil to gasoline. One of the important aspects of of this second series are reported in Table II the invention is the effect on gasoline to coke ratio. below.

Activation of used catalyst 4 Cracking Yields 1.1? Fluorine s;;s i i s i g .31 332%]: G c 1: 1 Gssoli G 11 0!) 011 61' en es a8 0 9 s ne 380 no p wt. y cycles Per'Cent Per Cent Gasoline, to Coke to Gas wt. wt. Per Cent Ratio Ratio vol.

Standard Gas OiL Nil 3 a 4.4 1.8 sea 11:. 1:1 e.4=1 Gas 011... 0.28 a s 12.3 3.2 33.9 mm 2.11:1 Standard Gas 011.. Nil 13 5.4 31.0 18. 5:1 I am Treated Gas 011... 0.28 4 17 14.5 3.4 38.3 mm 2.0:1 Standard Gas 011-- Nil 3 20 5.2 2.0 10.3 20.111 7.1=1 Treated Gas 011... 0.28 e 2e 13.5 as see 11.s:1 2.11:1 Standard Gas 011 Nil 1 as 5.1 4.2 40.9 0.81 8.011

Table IIillustratesthe possibility of OVBItlGiiL- amount of propyl fluoride had been dissolved. ing. After the first series with fluoride contain- The results appear in Table m below.

Team 111 Activation of fresh catalyst Cracking Yields Flourlne Charge Stock, Content, No. of $535 410 F.

Description Per Cent Cycles 016's Gas, Coke, E. P. Gasoline Gasoline 4 wt. y. Per Cent PerCent Gasoline, to Coke to Gas wt. wt. Per Cent Ratio Ratio vol.

Standard Gas 01L Nil 5 5 0.5 2.9 43.0 14.8:1 0.6:1 Treated Gas 0ll 0.20 5 10 14.8 4.5 47.4 10. 5:1 3. 2:1 Standard Gas Oil. Nil 4 14 7.7 3.2 48.0 15.0:1 6.2:1 ing oil, the activity, gasoline to coke ratio and Tables IV, V, VI, and VII below show further gasoline to gas ratio were all improved to a the .eifect of organic fluorides on cracking catmarked extent. The second series of treatment alysts. The bead catalyst of Table IV was with fluorides yielded some improvement, but the prepared according to the disclosure of Patent third series resulted in an overall deterioration of No. 2,385,217, dated September 18, 1945, t M11- the catalyst. While the activity was slightly inton M. Marisic. That process involves injectingcreased, the more than 50% reduction in the gasa, g'elable silica-alumina sol into a body of oil oline to coke ratio is regarded as serious loss in in which globules of the sol assume spherical economic value of the catalyst. 40 shape and set to firm spheroids which are then To illustrate that the eflect obtained is attribwashed and dried to hard glassy beads of catutable to organic fluorides in the charge stock, a alyst. The natures of the catalysts of the other series was run using a gas oil in which a small tables are sufllciently indicated in the tables.

TABLE IV Activation of fresh and used synthetic bead catalyst Cracking Data 1 glugrhte N i gi i 410 on an o. 0 vs 0. Charge swck' Desmptm Per Cent Cycles of Gas, Coke, r. n. r. Gasoline Gasoline wt. Cycles Per Cent Per cent Gasoline, to Coke to Gas wt. wt. Per Cent Ratio Ratio vol.

FRESH BEAD CATALYST Standard Gas Oil (a) Nil 3 3 7. 0 3. 2 45.3 14. 2 e. 5 Naphtha plus Isopropyi Fluoride (b). 0. l2 1 4 Standard Gas Qil (a) Nil 5 9 0.4 3. 8 50.4 13.2 7. 9

USED BEAD CATALYST Standard Gas 011 (a) Nil 5 5 I 6. 0 2. 7 39. 8 14. 7 6. 6 Standard Gas Oil plus Isopropyl luoride (a) 0.1 to 0.2 5 l0 8.8 3.3 48.5 14.7 5.5 Standard Gas Oil (a) Nil 6 l5 0. 1 3. 2 46.4 14. 6 7. 6 Standard Gas Oil plus Isopropyl Fluoride (a) 0.1 to 0.2 5 20 9. 6 4. 0 49. 2 12.3 5. 1 Standard Gas Oil (a) Nil 4 24 6. 5 3.4 47. 9 14. I 7. 4

I Cracking Conditions:

Runs Marked Temp., F 800 800 Space Velocity, V./V./hr 1. 5 3. 0 Catalyst t'o Oil Ratio, vol 4:1 1:1 Pressure, P. S. I. G 0 0 t None None Tssuv Activation of fresh and used Superjlltml pellet catalysts 0mm sunk. Dena-lotion Fluorine Content,

Per Cent wt.

Cumula- No. of tlve N o. Cycles of Cycles Gas, Per Cent Cracking Data 1 41 Coke, F. Gasoline Per cent Gasoline, to Coke wt. Per clent Ratio FRESH SUPERFILTROL PELLET CATALYST N11 3 4. 1 0. l2 2 O. 9 Nil 5 3. 6 Naphlha plus Isopmpyl Fluoride 0.12 1 0. 3 Stnndu'd Gas Oil (1:) Nil 6 4. 0

USED SUPERFILTROL PELLET CATALYST Standard Gas Oil (0 Nil 5 5 3. 2 2. 5 27. 6 11.0 8. 6 Naphtha plus Isopropyl Fluoride (c). 0. 12 3 8 O. 6 Standard Gas 011 (a) Nil 5 13 3. 4 3. 4 32. 0 10. 7 9. 4 Naphtha plus Isopropyi Fluoride (0).... 0. 12 3 21 0. 6 Standard Gas Oil (0) Nil 3 24 3.3 2. 4 33. 3 13.9 10. 1

l Cracking Conditions:

Runs Marked o b c Temp. F 800 800 800 Space mom ,V./V.ihr- 1. a 3. o 3. 0 Catalyst to O lBatio, v 4:1 2:1 1:1 Pressure, P. S. I. G 0 0 0 Steam None None None TABLI VI Activation of fresh jullers earth pellet catalyst Cracking Data l on an o. 0 ve o. Wampum Per ceni c cles of Gas, Coke, F. E. P. Gasoline 088011116 wt. Cycles Per Cent Per eent Gasoline, to Coke to Gas wt. wt. Per Cent Ratio Ratio .vol.

Standard G on (a)-.. Nil 4' 4 2. 2 1. s 18.5 10. 3 8. 4 Naphtha plus Ieopropyl 0. 12 L 5 1- 0 Standard Gas Oil (a) Nil 3 8 2.4 2. 0 19.0 9. 5 7. 9 Naphtha plus Isopropyl Fluoride (b). 0. 12 1 9 1. 0 Standard Gas Oil Nil 4 13 I 2. 6 1. 9 21. 8 11. 5 8. 4 Naphthaplus Isopropyl Fluoride (0).... 0.12 1 '14 1.3 Standard Gas Oil a Nil 3 17 3.0 2.3 23.1 10.0 7. 7 Naphtha plus Ieopropyl Fluoride (0).... 0. 12 2 19 1. 2 Standard. Gas 011 (a) 4 3. 0 2. 8 26.3 9. 4 8. 8

I Cracking Conditions:

Runs Marked Temp., F 800 800 Space Velocit ,VJVJhr 1.5 3.0 Catalyst to 0 1 Ratio, voL. 4:1 1:1 Pressure, P.S.1. 0 0 Steam None None Same, Activated, Steam-Treated TasuVlI Eflect of steam treatment on crackinoactlvities of catalysts before and after activation as in Tables IV, V and VI 1 Cracking mw Cycles Gas, per

('Joke,t per con Gasoline to Coke Ratio B thetic Pellet Catalyst 8:1 :19, Activated Sarge, Activated, flteam-Treatodrlieac tivat Same, Steam-Treated Used Bead Catalyst Same, Activated Same. Activated, Steam-Treatoi.-- Same. Steam-Treated Fresh Superflltrol Pellet Catalyst--- Same. Activated Same, Activated Steam-Treated cauaecumaweaupcupcc, Q OIQ Same, Steam-Treated H H a caas ocaarmau fi cocoon as a-s-aassawaswr NP? 1 All steam treatments made using 10% steam at 105 F. (or 6 hours.

T p" Space velocit ,V .11

Catalyst to o lrat 0, vol Pressure, P. S. I. G

team

:1 0 None Particular attention is called to the fact that steam treatment of activated synthetic catalysts results in outstanding gasoline to coke and gasoline to gas ratios.

We claim:

1. In a process for conversion of hydrocarbons wherein hydrocarbon vaporsare contacted with a solid porous catalyst containing silica and alumina for a predetermined period of time to convert said hydrocarbons with concurrent deposition of a combustible deposit on the catalyst which substantially lowers the catalytic efllciency thereof, followed by burning regeneration of the catalyst and return of th catalyst to conversion of hydrocarbons thus completing a cycle of operation which is repeated until the catalyst is deactivated to a substantial extent by eifects other than said combustible deposit as evidenced by the fact that burning regeneration of the catalyst alter a series of cycles regenerates the catalyst to an activity as measured by per cent conversion of said hydrocarbons lower than the activity of the catalyst at the beginning of said series; the improvement which comprises contacting said catalyst in at least one cycl with a hydrocarbon vapor containing a small amount, not more than about 3% by weight, of organic fluorides and after contacting said catalyst with said fluoride containing vapor, again contacting hydrocarbon vapor substantially free of fluorides with said catalysts.

2. In a process for conversion or hydrocarbons wherein hydrocarbon vapors are contacted with a, solid porous catalyst containing silica and alumina for a predetermined period of time to convert said hydrocarbons with concurrent deposition of a combustible deposit on the catalyst which substantially lowers the catalytic efliciency thereof, followed by burning regeneration of the catalyst and return of the catalyst to conversion of hydrocarbons thus completing a cycle of operation which is repeated until the catalyst is deactivated to a substantial extent by eflects other than said combustible deposit as evidenced by the fact that burning regeneration ofthe catalyst after a series of cycles regenerates the catalyst to an activity as measured by per cent conversion of said hydrocarbons lower than the activity of the catalyst at the beginning of said series; the improvement which comprises contacting said catalyst in at least one cycle with hydrocarbon vapor containing a, small amount, not more than about 3% by weight, of organic fluorides, thereafter contacting said catalyst with steam to thereby improve the gasoline to coke and gasoline to gas ratios, and after contacting said catalyst with said fluoride containing vapor and said steam,

again contacting hydrocarbon vapor substantially tree of-fluorldes with said catalyst.

3. In a process for conversion of hydrocarbons wherein hydrocarbon vapors are contacted with a solid porous catalyst containing silica and alumina for a predetermined period of time to convert said hydrocarbons with'concurrent deposition of a combustible deposit on the catalyst which substantially lowers the catalytic efllciency thereof, followed by burning regeneration of the catalyst and return of the catalyst to conversion of hydrocarbons thus completing a cycle of operation which is repeated until the catalyst is 'deactivated to a, substantial extent by eflects other than said combustible deposit as evidenced by the fact that burning regeneration oi. the catalyst after a series of cycles regenerates the catalyst to an activity as measured by per cent conversion of said hydrocarbons lower than the activity of the catalyst at the beginning of said series; the improvement which comprises contactlng said catalyst in at least one cycle with a hydrocarbon vapor containing a small amount, by weight, of proypl fluoride and after contacting said catalyst with said fluoride containing vapor, again contacting hydrocarbon vapor substantially tree. of fluorides with said catalyst. a

4. In a process for conversion of hydrocarbons wherein hydrocarbon vapors are contacted with a solid porous catalyst containing silica and alumina for a predetermined period of time to convert said hydrocarbons with concurrent deposition of a combustible deposit on the catalyst which substantially lowers the catalytic efiiciency thereof, followed by burning regeneration of the catalyst and return of the catalyst to conversion of hydrocarbons thus completing a cycle of operation which is repeated until the catalyst is deactivated to a substantial extent by eflects other than said combustible deposit as evidenced by the fact that burning re- I generation of the catalyst after a series of cycles regenerates the catalyst to an activity as measured by per cent conversion of said hydrocarbons lower than the activity of catalyst at the beginning of said series; the improvement which comprises contacting said catalyst in at least one cycle with a hydrocarbon vapor containing a small amount, not more than about 1% by weight, of organic fluorides and after contacting said catalyst with said fluoride containing vapor, again contacting hydrocarbon vapor substantially free of fluorides with said catalyst.

5. In a process for conversion of hydrocarbons wherein hydrocarbon vapors are contacted with a solid porous catalyst containing silica and alumina, for a predetermined period of time to convert said hydrocarbons with concurrent denosition of a combustible deposit on the catalyst which substantially lowers the catalytic efilciency thereof, followed by burning regeneration of the catalyst and return of the catalyst to conversion of hydrocarbons thus completing a. cycle of operation which is repeated until the catalyst is deactiviated to a substantial extent by effects other than said combustible deposit as evidenced by the fact that burmng regeneration of the catalyst after a series of cycles regenerates the catalyst to an activity as measured by per cent conversion of said hydrocarbons lower than the activity of the catalyst at the beginning of said series; the improvement which comprises contacting said catalyst in at least one cycle with hydrocarbon vaporcontaining a small amount, not more than about 1% by weight, of organic fluorides, thereafter contacting said catalyst with steam to. thereby improve the gasoline to coke and gasoline to gas ratios, and after contacting said catalyst with said fluoride containing vapor and steam, again contacting hydrocarbon vapor substantially free of fluorides with said catalyst as aforesaid.

6. In a process for conversion of hydrocarbons wherein hydrocarbon vapors are contacted with a, solid porous catalyst containing silica, and alumina for a predetermined period of time to convert said hydrocarbons with concurrent deposition of a combustible deposit on the catalyst which substantially lowers the catalytic efllciency thereof, followed by burningregeneration of the catalyst and return of the catalyst to conversion of hydrocarbons thus completing a cycle of operation which is repeated until the catalyst is deactivated to a substantial extent by eflects other than said combustible deposit as evidenced by the fact that burning regeneration of the catalystafter a series of cycles regenerates the catalyst to an activity as measured by per cent con version of said hydrocarbons lower than the activity of the catalyst at the beginning of said series; the improvement which comprises contacting said catalyst in at least one cycle with'a hydrocarbon vapor containing a small amount, not more than about 1% by weight, of propyl fluoride, and after contacting said catalyst with said fluoride containing vapor, again contacting hydrocarbon vapor substantially free of fluorides with said catalyst.

7. In a process for conversion of hydrocarbons wherein hydrocarbon vapors are contacted with a solid porous catalyst containing silica and a difficultly reducible metal oxide for a predetermined period of time to convert said hydrobons with concurrent deposition of a combustible deposit on the catalyst which substantially lowers the catalytic efliciency thereof, followed by burning regeneration of the catalyst and return of the catalyst to conversion of hydrocarbons thus completing a cycle of operation which is repeated until the catalyst is deactivated to a substantial extent by effects other than said combustible deposit as evidenced by the fact that burning regeneration of the catalyst after a series of cycles regenerated the catalyst to an activity as measured by per cent conversion of said hydrocarbons lower than the activity of catalyst at the beginning of said series; the improvement which comprises contacting said catalyst in a plurality of cycles with a. hydrocarbon vapor-containing a small amount, not more than about 0.3% by weight, of organic fluorides and after contacting said catalyst with said fluoride containing vapor, again contacting hydrocarbon vapor substantially free of fluorides with said catalyst.

8. In a process for conversion of hydrocarbons wherein hydrocarbon vapors are contacted with a solid porous catalyst containing silica and a diflicultly reducible metal oxide for a predetermined period of time to convert said hydrocarbons with concurrent deposition of a combustible deposit on the catalyst which substantially lowers the catalytic efficiency thereof. followed by burning regeneration of the catalyst and return of the catalyst to conversion of hydrocarbons thus completing a cycle of operation which is repeated until the catalyst is deactivated to a substantial extent by effects other than said combustible deposit as evidenced by the fact that burning regeneration of the catalyst after a series of cycles regenerates the catalyst to an activity as measured by per cent conversion of said hydrocarbons lower than the activity of the catalyst at the beginning of said series; the improvement which comprises contacting said catalyst in a plurality of cycles with hydrocarbon vapor containing a small amount, not more than about 0.3% by weight, of organic fluorides, thereafter contacting said catalyst with steam to thereby improve the gasoline to coke and gasoline to gas ratios, and after contacting said catalyst with said fluoride containing vapor and steam, again contacting hydrocarbon vapor substantially free of fluorides with said catalyst as aforesaid.

9. In a process for conversion of hydrocarbons wherein hydrocarbon vapors are contacted with a solid porous catalyst containing silica and a difficultly reducible metal oxide for a predetermined period of time to convert said hidrocarbons with concurrent deposition of a combustible deposit on the catalyst which substantially lowers the catalytic efficiency thereof, followed by burning regeneration of the catalyst and return of the catalyst to conversion of hydrocarbons thus completing a cycl of operation which is repeated until the catalyst is de- 2,430,785 v 13 14 activated to a substantial extent by effects other UNITE than said combustible deposit as evidenced by D STATES PA 8 the fact that burning regeneration of the cat- Number N me Date alyst after a series of cycles regenerates the cat-- 2,309,137 Peterkin Jan. 26, 1943 aiyst to an activity as measured by per cent 5 2,31 ,317 Roberts Feb. 9, 1943 conversion of said hydrocarbons lower than the 2,336,165 C nol y .Dec. '1, 1943 activity of the catalyst at th beginning of said 37,640 Burgin Dec. 28, 1943 series; the improvement which comprises con- 2,350,159 o ins et y 4 tasting said catalyst in a plurality of cycles with ,371,341 Matuszak Mar. 13, 1945 a hydrocarbon vapor containing a small amount, 10 2, 10, 27 Sweeney Feb. 9, 1943 not more than about 0.3% by weight, of propyl 7 Fr y Mar. 27, 45 fluoride, and after contacting said catalyst with 2, 78,763 Frey June 19. 1945 said fluoride containing vapor, again contacting ,387,309 Sweeney Oct. 23, 1945 hydrocarbon vapor substantially free of fluorides with said catalyst. 15 OTHER FREDERICK Grosse and Linn, "The Addition of Hydrogen RUSSEIL LEE Fluoride to the Double Bond, Jour. of Organic JACOB MEAD0W Chemistry, vol. III, 1938, pages 26-32. (Copy in Pat. Ofl. Lib.) REFERENCES orrm w The following references are of record in the flle of this patent: 

